This invention relates to aromatic compounds and more particularly to aromatic compounds containing nitro groups.
2,2',4,4',6,6'-hexanitrostilbene (HNS) is an explosive which is used in explosive actuating devices, detonating cords, flexible shape charges, etc. The HNS-I which is produced by conventional methods is crude and contains substantial amounts of hexanitrobibenzyl as an impurity. As a result, crude HNS-I has poorer thermal stability properties than HNS-II. Washing the crude produce with solvent only removes the surface contaminents; impurities which have cocrystallized or occluded with the product HNS-I are not removed. Another approach is to digest the crude HNS-I by heating it in organic solvents; however, crystal growth occurs during this process and a wide particle size distribution results. Yet another method of purification is to dissolve the crude HNS-I in hot fuming nitric acid and then allow the solution to slowly cool to room temperature. This method produces a purer larger particle HSN-II. U.S. Pat. No. 4,260,837 discloses a method of producing purer small particle HNS-I by dissolving crude HNS-I in hot fuming nitric acid and then drowning the HNS-nitric acid solution in water. Unfortunately, these last two methods produce HNS crystals which are slightly contaminated with nitric acid and which therefore have lower thermal stabilities than is necessary for many applications.